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<head><meta charset="utf-8"><title>nightly-2020-10-06 regression with Deref/(blanket impls?) · t-compiler · Zulip Chat Archive</title></head>
<h2>Stream: <a href="https://rust-lang.github.io/zulip_archive/stream/131828-t-compiler/index.html">t-compiler</a></h2>
<h3>Topic: <a href="https://rust-lang.github.io/zulip_archive/stream/131828-t-compiler/topic/nightly-2020-10-06.20regression.20with.20Deref.2F(blanket.20impls.3F).html">nightly-2020-10-06 regression with Deref/(blanket impls?)</a></h3>

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<a name="212579123"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/131828-t-compiler/topic/nightly-2020-10-06%20regression%20with%20Deref/%28blanket%20impls%3F%29/near/212579123" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Tony Arcieri <a href="https://rust-lang.github.io/zulip_archive/stream/131828-t-compiler/topic/nightly-2020-10-06.20regression.20with.20Deref.2F(blanket.20impls.3F).html#212579123">(Oct 07 2020 at 15:51)</a>:</h4>
<p>We appear to have encountered a nightly regression where the compiler is failing to find a trait impl through a... rather twisty maze of things like <code>Deref</code>, multiple layers of traits bounds,  and blanket impls:</p>
<p><a href="https://github.com/informalsystems/tendermint-rs/pull/584#issuecomment-704777178">https://github.com/informalsystems/tendermint-rs/pull/584#issuecomment-704777178</a></p>
<p>I can try to put together a minimal repro (I have it reproduced locally building the <code>ecdsa</code> crate) but before I do, I was wondering if it's already known .</p>
<p>The issue is <em>NOT</em> present in <code>nightly-2020-10-05</code></p>



<a name="212579273"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/131828-t-compiler/topic/nightly-2020-10-06%20regression%20with%20Deref/%28blanket%20impls%3F%29/near/212579273" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Tony Arcieri <a href="https://rust-lang.github.io/zulip_archive/stream/131828-t-compiler/topic/nightly-2020-10-06.20regression.20with.20Deref.2F(blanket.20impls.3F).html#212579273">(Oct 07 2020 at 15:52)</a>:</h4>
<p>another clue: explicitly <code>Deref</code>-ing the type in question using <code>*myval</code> fixes the problem</p>



<a name="212579388"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/131828-t-compiler/topic/nightly-2020-10-06%20regression%20with%20Deref/%28blanket%20impls%3F%29/near/212579388" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jonas Schievink  [he/him] <a href="https://rust-lang.github.io/zulip_archive/stream/131828-t-compiler/topic/nightly-2020-10-06.20regression.20with.20Deref.2F(blanket.20impls.3F).html#212579388">(Oct 07 2020 at 15:53)</a>:</h4>
<p>probably the same cause as <a href="https://github.com/rust-lang/rust/issues/77638">https://github.com/rust-lang/rust/issues/77638</a></p>



<a name="212579429"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/131828-t-compiler/topic/nightly-2020-10-06%20regression%20with%20Deref/%28blanket%20impls%3F%29/near/212579429" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Tony Arcieri <a href="https://rust-lang.github.io/zulip_archive/stream/131828-t-compiler/topic/nightly-2020-10-06.20regression.20with.20Deref.2F(blanket.20impls.3F).html#212579429">(Oct 07 2020 at 15:53)</a>:</h4>
<p>aha</p>



<a name="212579489"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/131828-t-compiler/topic/nightly-2020-10-06%20regression%20with%20Deref/%28blanket%20impls%3F%29/near/212579489" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Tony Arcieri <a href="https://rust-lang.github.io/zulip_archive/stream/131828-t-compiler/topic/nightly-2020-10-06.20regression.20with.20Deref.2F(blanket.20impls.3F).html#212579489">(Oct 07 2020 at 15:53)</a>:</h4>
<p>will keep an eye on that issue. thanks</p>



<hr><p>Last updated: Aug 07 2021 at 22:04 UTC</p>
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